Student Linked List

C program to construct a singly linked list consisting of following instructions in each node : 1.Student ID(int) 2.Student name(string) 3.Semester(int) The operations supported are 1.Insertion operation at any position 2.deleting a node based on ID

#include<stdio.h>
#include<stdlib.h>

typedef struct node
{
 char name[25];
 int id,sem;
 struct node *link;
}NODE,*NODEPTR;

NODEPTR insertp(NODEPTR start,int pos, int *count)
{
 NODEPTR temp,prev,cur;
 int i;
 temp=(NODEPTR)malloc(sizeof(NODE));
 if(temp==NULL)
  printf("Memory allocation not possible\n");
 printf("Enter the name, ID and semester of the student\n");
 scanf("%s%d%d",temp->name,&temp->id,&temp->sem);
 temp->link=NULL;
 for(cur=start;cur!=NULL;cur=cur->link)
  if(cur->id==temp->id)
  {
    printf("ID already exists\n");
    free(temp);
    return start;
   }
 (*count++);
 if(pos==1)
 {
   temp->link=start;
   start=temp;
   return start;
 }
 cur=start;
 for(i=1;i<pos;i++)
 {
   prev=cur;
   cur=cur->link;
  }
 prev->link=temp;
 temp->link=cur;
 return start;
}

NODEPTR deleteid(NODEPTR start, int did, int *count)
{
  NODEPTR prev,cur;
  for(cur=start;cur!=NULL;prev=cur,cur=cur->link)
  {
    if(cur->link==did)
      break;
  }
  if(cur==NULL)
  {
    printf("Record not found\n");
    return start;
  }
 if(cur==start)
  start=start->link;
 else
  prev->link=cur->link;
 free(cur);
 (*count)- -;
 return start;
}

int search (NODEPTR start, int sid)
{
  NODEPTR cur,t;
  int mid;
  for(cur=start;cur!=NULL;cur=cur->link)
    if(cur->id==sid)
      break;
  if(cur==NULL)
   printf("Record not found\n");
 else
 {
   while(1)
   {
     printf("Enter the ID of the student to be searched\n");
     scanf("%d",&nid);
     for(t=start;t!=NULL;t=t->link)
     {
       if(nid=t->id && (nid!= cur->id))
       {
         printf("ID already exists, enter again\n");
         break;
        }
     }
     if(t==NULL)
     {
       cur->id=nid;
       printf("Enter the name and semester\n");
       scanf("%s%d",cur->name,&cur->sem);
       return;
     }
    }//end of while
   }//end of else
 }//end of function

void display(NODEPTR start)
{
  NODEPTR cur;
  if(start==NULL)
   printf("The list is empty\n");
 else
 {
   printf("List content is shown below\n");
   for(cur=start;cur!=NULL;cur=cur->link)
     printf("%s\t%d\t%d\n",cur->name,cur->id,cur->sem);
  }
}

int main()
{
  NODEPTR start=NULL;
  int ch, id, pos, count=0;
  while(1)
  {
    display(start);
    printf("Enter your choice of operation 1.Insert 2.Delete 3.Search OTHER:Exit\n");
    scanf("%d",&ch);
    switch(ch)
    {
      case 1 : printf("Enter the position (1 to %d) to insert the node\n", count+1);
                   scanf("%d",&pos);
                   if(pos < 1 || pos>count+1)
                      printf("Invalid position\n");
                   else
                      start=insertp(start,pos,&count);
                  break;
     case 2 : printf("Enter the ID to be deleted\n");
                  scanf("%d",&id);
                  start=deleteid(start,id,&count);
                  break;
    case 3 : printf("Enter the ID to be searched\n");
                 scanf("%d",&id);
                 search(start,id);
                 break;
   default : return;
  }
 }
}